Physical antimicrobial method is a traditional method for preventing infections and spread of pathogenic microorganisms. Common physical antimicrobial methods include high temperature, high pressure and ultraviolet sterilization methods, etc. But these traditional physical antimicrobial methods are harmful when directly used in the human body, so they are essentially used to disinfect objects and spaces, unused in the human body. Generally antimicrobial methods for human body can only rely on a variety of antimicrobial agents.
At present, antimicrobial methods for use in human body are chemical and biological methods, in which antimicrobial agents exert antimicrobial action by the mechanisms selected from preventing the synthesis of bacterial cell wall, affecting the function of cell membranes, inhibiting protein synthesis, and affecting the metabolism of nucleic acids and folic acid etc. These mechanisms can achieve antimicrobial function only by antimicrobial drugs binding to pathogenic microorganisms and even entering the body thereof. The clinical use of antimicrobial drugs, especially the abuse of antimicrobial drugs results in the production of a large number of drug-resistant strains, and thus becomes an important problem to hinder clinical medical development.
In addition to traditional antimicrobial methods, there are some new antimicrobial methods at present, such as nano-silver antimicrobial and so on. In nano-silver dressing, Ag+ kills pathogenic microorganisms by penetrating cell membrane. This mechanism is similar to chemical antimicrobial principle, and damages normal human cells, and may have drug resistance when used topically.
Classical microbiology is against planktonic bacteria. However, with further study on bacteria and infections, it has been found that in nature, in some industrial environment and in and outside human and animal body, majority of bacteria are attached to the surface of living or non-living objects, growing in biofilm (BF) manner not in planktonic mode. Biofilm is formed by enclosing bacteria with extracellular matrix to form special structure such as honeycomb-shape with very complex ecosystem in which bacteria can exchange information (see, for example Donlan, R. M., Biofilms and device-associated infections, Emerg. Infect. Dis, 2001.7, 277-281; C. Schaudinn, P. Stoodley, A. Kainovic, T. O'Keefe, B. Costerton, D. Robinson, M. Baum, G. Erlich, and P. Webster, Bacterial biofilms, other structures seen as mainstream concepts, Microbe, 2007 2, 231-237; and H.-C. Flemming, T. R. Neu, and D. J. Wozniak, The EPS Matrix, The “House of Biofilm Cells”, J. Bacteriol, 2007; 18 (22), 7945-7947). After the formation of the biofilm, bacteria can withstand washing, phagocytosis and antimicrobial agents (see, e.g. Trautner B W, Darouiche R O, Role of biofilm in catheter-associated urinary tract infection, AM J Infect Control, 2004, 32, 177-83 and Costerton J, Geesey G, Cheng K, How bacteria stick, Sci Am, 1978, 238, 86-95).
New methods have been studied to prevent and alter the formation of biofilm, including furanone, Furacilin, silver-containing preparations, etc. (see, for example J. R. Johnson, P. Delavari, and M. Azar, Activities of a nitrofurazone-containing urinary catheter and a silver hydrogel catheter against multidrug-resistant bacteria characteristic of catheter-associated urinary tract infection, Antimicrob. Agents Chemother, 1999, 43, 2990-2995; J. R. Johnson, T. Berggren, and A. J. Conway, Activity of a nitrofurazone matrix urinary catheter against catheter-associated uropathogens, Antimicrob Agents Chemother, 1993, 37, 2033-2036; P Tenke, B Kovacs, Bjerkl and T E Johansen, et al, European and Asian guidelines on management and prevention of catheter-associated urinary tract infections, Int J Antimicrob Agents, 2008; Vol. 31, Suppl 1, pp S68-78; and Kunin C M, Nosocomial urinary tract infections and the indwelling catheter: what is new and what is true? Chest. 2001, 120, 10-12). However, these methods also have some drawbacks.
Thus, it is still desirable to provide novel antimicrobial methods and relevant preparations capable of avoiding drug resistance.